Synthesis and characterization of ceria quantum dots using effective surfactants

The stable and crystalline phase of different surfactants (CTAB, PEG and SDS) capped CeO₂ nanoparticles were directly synthesized by chemical precipitation method at room temperature. The effects of surfactants on the structural and optical properties of nanoparticles are characterized. The optical properties of the nanoparticles were investigated by UV–visible and PL spectroscopy. The effects of surfactants with observed band shifts are due to quantum confinement effect. The optical band gap values are determined by simple energy wave equation and Tauc plot method. The observed particle sizes are very closer to the Bohr exitonic radius. The emission bands such as violet, blue, green and orange are observed in PL spectra. The PL integrated intensity ratio of the UV emission to the deep-level green emission (I_UV/I_DLE) for CTAB, PEG and SDS capped CeO₂ nanoparticles are observed. The XRD measurement shows that CeO₂ has cubic fluorite structure having the particle size 6–10 nm. The lattice strains were detected by Williamson–Hall plot method. The surface morphology of the nanoparticles is studied by SEM and FESEM analysis. TEM images show that the particles are nearly spherical in shape with diameter of 5–10 nm. Using FTIR spectra, the functional groups of the ceria are identified.     

Novel Thermally-Accessible Structural Changes of Chiral and Some Related Cu（ll） Complexes

A mononuclear chiral copper（ll） complex, [Cu（RRchxn）2（C（CN）3）2]＇H20 （RRchxn = （1R, 2R）-diaminocyclohexane） （RRchxnH）, and its deuterated compound, [Cu（RRchxn）2（C（CN）3）z].D20 （RRchxnD）, and their isomers, [Cu（trchxn）2（C（CN）3）2]＇H20 （trchxn = trans-l,2-diaminocyclohexane） （trchxnH） and [Cu（trchxn）2（C（CN）3）2]＇D20 （trchxnD） have been prepared and characterized by means of 1R （infrared）, electronic, and CD （circular dichroism） spectra, magnetic susceptibility, and variable-temperature X-ray crystallography as single crystals or powder. Interestingly, depending on grain size of samples, RRchxnH exhibits the monoclinic form and the orthorhombic form, which are distinguished by systematic absence and powder XRD （X-ray diffraction） patterns clearly. Although single crystals did not exhibit phase transition, powder XRD patterns of RRchxnH and weakly hydrogen bonded RRchxnD emerged low-temperature phase of monoclinic in the orthorhombic patterns only around 200-220 K. However, as a control, powder XRD patterns of both trchxnH and trchxnD did not exhibit such phase transition clearly.     

Design and statistical analysis of plasma coatings on superalloy for gas turbine applications

The Influence of plasma sprayed NiCr–Cr₂O₃ and Al₂O₃–40% TiO₂ (A40T) coatings on Inconel 617 are investigated at 900 and 1000 °C under mixed salt environment for gas turbine applications. The results revealed that the plasma coated alloy exhibits lower mass change than bare alloy in the Na₂SO₄ and NaCl salt mixture with and without V₂O₅. The response to the experimental analysis is statistically evaluated using 2³ factorial design. Further the exposed samples were analyzed by means of optical image, SEM, EDS and XRD results. The EDS and XRD analysis revealed that the oxides are rich in Ni and Mo on the surface of the samples. The coated samples exhibited better corrosion resistance in A40T when compared to NiCr–Cr₂O₃ coatings than bare alloy.     

Effect of NaOH activation on sulphate resistance of GGBFS and binary blend pastes

This paper presents an investigation into the observed enhanced performance that alkali activated ground granulated blast furnace slag (GGBFS) and binary blends offer against sulphate attack. X-ray diffraction (XRD) was carried out to identify and quantify the crystalline phases formed in a wide range of GGBFS and GGBFS-OPC (ordinary Portland cement) blends. Furthermore, specimens were exposed to a sulphate solution to examine the evolution of compressive strength along with identification of activation and/or hydration products. XRD demonstrated that ettringite was completely decomposed into its constituents in the presence of NaOH while quantification ascertained the formation of considerable amounts of hydrotalcite in the activated GGBFS and binary blends. Alkali activated GGBFS and binary blends specimens with higher GGBFS content offered enhanced resistance against aggressive sulphate ions and no significant degradation products were observed in these specimens after 6 months of exposure to sulphate solution. The results demonstrated that hydrotalcite formation may be a major reason for the improved sulphate resistance of alkali activated GGBFS and binary blend pastes with higher GGBFS content.     

Comparative Nutritional,Functional, Morphological,and Diffractogram Study on Culinary Banana (Musa ABB) Peel at Various Stages of Development

The culinary banana peel, which is an agricultural waste available in abundance, has not been able to draw much attention in terms of its utilization. In addition to being an abundant source of functional and nutritional compounds, it also deserves to be utilized in a proper and/or better way. The aim of this study was to explore this agro-waste at different levels of maturity in order to identify the active compounds at particular stage of maturity. Phenolics, flavonoids, and radical scavenging activity were maximum at early developmental stage, whereas compounds like protein, fat, carbohydrates, and starch increased with maturity and declined at over-ripe stage. The starch present in the peel is of C-type as confirmed by x-ray diffractograms and crystalline in nature. The peel, at the edible mature stage 4, yielded a high cellulose content which could be used as a reinforcement material in high-performance biocomposites. The presence of various functional groups indicating the complex nature of the culinary banana peel was confirmed by Fourier transform infrared characterization. Scanning electron microscope micrographs revealed that microstructure of peel changes drastically and degradation of starch and other compounds occurred at the over-ripe stage. Hence, in this context, the culinary banana peel can serve as a potential biomaterial in industrial applications and can add a higher value to this locally important and underutilized crop.     

Effect of cooling methods on residual compressive strength and cracking behavior of fly ash concretes exposed at elevated temperatures

This paper presents the effects of cooling methods on residual compressive strength and cracking behavior of concretes containing four different class F fly ash contents of 10%, 20%, 30% and 40% as partial replacement of cement at various elevated temperatures. The residual compressive strength of the aforementioned fly ash concretes is measured after being exposed to 200, 400, 600 and 800 °C temperatures and two different cooling methods, for example, slow cooling and rapid water cooling. Results show that the residual compressive strengths of all fly ash concretes decrease with increase in temperatures irrespective of cooling regimes, which is similar to that of ordinary concrete. Generally, control ordinary concrete and all fly ash concretes exhibited between 10% and 35% more reduction in residual compressive strength because of rapid cooling than slow cooling except few cases. Cracks are observed over concrete specimens after being exposed to temperatures ranging from 400 to 800 °C. Samples that are slowly cooled developed smaller cracks than those rapidly cooled. At 800 °C, all fly ash concretes that are exposed to rapid cooling showed the most severe cracking. X‐ray diffraction analysis shows reduction of Ca(OH)₂ peak and formation of new calcium silicate peak in concretes containing 20% and 40% fly ash when subjected to 800 °C in both cooling methods. Thermo gravimetric analysis and differential thermal analysis results show increase in thermal stability of concrete with increase in fly ash contents. The existing Eurocode also predicted the compressive strength of fly ash concretes with reasonable accuracy when subjected to the aforementioned elevated temperatures and cooling methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of near infrared sensors to preconcentration of hydrothermally-formed copper ore

Near infrared sensors can be a very useful technique for the qualitative analysis of complex ores, and thus could be useful for the preconcentration of ores. In this paper, individual particles of hydrothermally-formed copper ore sampled from a mine in the Los Pozos mining district, northern Chile, were classified as product, middling and waste based on their near infrared response. The classification of copper bearing minerals (product) from gangue (waste) was considered for vibration combination bands at longer wavelengths from 2000 to 2400 nm. This region exhibits characteristic features for carbonates and hydroxyl gangue bearing minerals. The near infrared features at 1400 and 1900 nm were not considered favourable for classification and subsequent discrimination because they can be influenced by moisture and other environmental factors and are easily suppressed by iron-rich minerals.Two near infrared preconcentration strategies were applied for particle discrimination. Results indicate that targeting only the calcite (carbonate) dominated particles for discrimination as waste provided the best option for preconcentration. The near infrared discrimination analysis correlates well with mineralogical (QEMSCAN® and XRD) and elemental (XRF) data classification. The results indicate that near infrared spectroscopy is a suitable preconcentration method for supergene copper ore.     

Precipitation Behavior of Modified as Cast High Nitrogen Super Hard High‐Speed Tool Steel

The properties of high‐speed tool steels can be improved by modifying their chemical composition or the technology of production. Nitrogen alloying is an attractive technology to enhance the mechanical and physical properties of tool steels. In this work, modified super hard high‐speed tool steel was produced through nitrogen alloying and decreasing the level of cobalt content in investigated steels. This work aims to study the effect of nitrogen as alloying element on carbides and carbo‐nitrides precipitates type, shape, and size for investigated steels. From the results obtained from Thermo‐Calc, it was concluded that nitrogen alloying produced large amount of stable austenite, also eutectic carbides precipitates (M₆C and M₇C₃) were stable at room temperature. Transmission electron microscope (TEM) images for traditional grade showed that the as cast structure contains beside the carbides network other single carbides precipitates. While on the other hand the selected area diffraction pattern (SADP) images of nitrogen alloyed grade shows fine carbides and carbo‐nitrides precipitates with more amount of retained austenite in the ferrite matrix, they showed also the presence of the eutectic precipitates as well as the dislocations.     

Hydrogenation and structural properties of Gd2Ni7 with superlattice structure

The crystal structure and hydrogenation properties of Ce₂Ni₇-type Gd₂Ni₇ were investigated by X-ray diffraction (XRD) and the hydrogen pressure–composition (P–C) isotherm. Ce₂Ni₇-type Gd₂Ni₇ was obtained by annealing at 1523 K for 12 h and quenching in ice water. Two superlattice reflections (002 and 004) of the Ce₂Ni₇-type were clearly observed at 2θ = 7.3° and 14.6° in the XRD profile. The refined lattice parameters were a = 0.49662(9) nm and c = 2.4255(3) nm, respectively. Two plateaus were clearly observed during the absorption–desorption process in the P–C isotherm. The first and second plateaus were at 0.015 and 0.13 MPa, respectively, in the first desorption. The maximum hydrogen capacity reached was 1.13 H/M. The enthalpy and entropy were calculated as −20 kJ/mol H₂ and −80 J/mol H₂ K, respectively, from the van’t Hoff plot. After the P–C isotherm, the GdNi₅ cell expanded by 2.15%, but the Gd₂Ni₄ cell shrank by 2.83%.